1. Field of the Invention
The present invention concerns networking in general, and wireless computer networks in particular.
2. Background Information
Recently, wireless networking components have been introduced that enable users to set up and use wireless local area networks (WLANs) that reduce or eliminate the installation of network cables that are necessary for conventional “land-line” computer networks, such as Ethernet networks. These WLANs are popular for use in buildings that are difficult to wire for conventional networking, such as homes and older office buildings, as well as for use in environments in which mobile computers are used and to extend the range of conventional wired networks.
Presently, there are four primary types of wireless network communication technologies, including Bluetooth, IrDA, HomeRF (SWAP) and WECA (Wi-Fi). Bluetooth provides a lower-cost solution that enables devices in close proximity to communicate using a radio channel. IrDA (Infrared Direct Access) is a standard for devices to communicate using infrared light pulses. This technology, which is used by most remote controls, is generally limited to shorter-range line-of-sight installations. HomeRF corresponds to an alliance of businesses that have developed a standard called Shared Wireless Access Protocol (SWAP). A sort of hybrid standard, SWAP includes six voice channels based on the Digital Enhanced Cordless Telecommunications standard and the IEEE 802.11 wireless-Ethernet specification for data. SWAP uses a technology known as frequency-hopping spread spectrum (FHSS), wherein short bursts of data are sent between frequency shifts (hops). SWAP networks are relatively inexpensive, in part because SWAP does not require an access point, but has limited bandwidth on the order of 1–2 Mbps (megabits per second).
The Wireless Ethernet Compatibility Alliance (WECA) has developed a wireless networking standard called Wi-Fi (wireless fidelity) based on the IEEE 802.11b specification. As with SWAP, Wi-Fi uses spread-spectrum radio waves in the 2.4-gigahertz (GHz) frequency range. However, Wi-Fi uses direct-sequence spread spectrum (DSSS) rather than FHSS to communicate by splitting each byte of data into several parts and sending them concurrently on different frequencies. This results in a bandwidth of up to 11 Mbps whenever an appropriate signal strength is available. If signal strength or interference results in disrupted data, Wi-Fi devices reduce their operating bandwidth to 5.5 Mbps, then 2 Mbps, and finally down to 1 Mbps to maintain network stability.
A Wi-Fi WLAN 10 is shown in FIG. 1. WLAN 10 includes a desktop personal computer (PC) station 12, an APPLE MACINTOSH G-3™ computer station 14, a UNIX workstation station 16, a tower PC station 18, a laptop station 20, and a laptop station 22, each of which is enabled to communicate with the other stations in the WLAN via a wireless access point (AP) 24. In many installations, a wireless AP will also provide a higher-speed network interface for connection to a conventional wired network, such as an Ethernet interface, to enable computers on a WLAN to also access a conventional wired LAN or WAN (wide area network). Accordingly, wireless AP 24 is shown in FIG. 1 as being connected to a network server 26 via an Ethernet link 28; however, it will be understood that a wireless AP may be implemented in configurations in which it is not connected to a LAN or WAN.
In order for a computer to communicate with a wireless AP, a computer may include a wireless network adapter that includes a transceiver designed to send and receive signals in a frequency range corresponding to the WLAN's operation type (e.g., 2.4 GHz frequency range for IEEE 802.11b WLANs). Typically, these wireless network adapters comprise a wireless network adapter card 30 for use in PCs and a PCMCIA wireless network adapter card 32 for use in laptops. Generally, modern APPLE™ computers may include a built-in “Airport” communication port to enable wireless network access, or implement a peripheral card in a manner similar to wireless network adapter card 30. Similar solutions are available for workstations.
An AP provides a basic and extended service set to one or more stations (i.e. computers) that communicate with the AP. The AP facilitates and coordinates communication and channel access between stations. Stations authenticated and associated with an AP typically do not operate in a peer-to-peer mode—communication from one station to another must route through the AP, as shown by communication paths 34, 36, 38, 40, 42, and 44. The AP serves as a relay station for data traffic between stations and, therefore, station-to-station communication takes at least twice the amount of time than if a source station could communicate directly with a target station (i.e., the source station must send data to the AP, which in turn resends the data to the target station). This results in the bandwidth of the wireless media being effectively reduced by half.
In addition to bandwidth reduction, there are other drawbacks common to AP-based wireless networks. One is cost—a typical access point may cost between $200–$1000+. In comparison, wireless network adapter cards cost much less ($70–$300). Another drawback is setup. Depending on the vendor, an AP-based WLAN may require assigning IP addresses to each of the computers in the network, which may also entail a manual configuration of each computer as well. In addition, there may be instances in which the range of the network may need to be extended, but this would require the purchase of an additional AP or an extension point (essentially an AP without a wired network interface) when implementing a conventional Wi-Fi-based WLAN.